1. Field of the Invention
Implementations of various technologies described herein generally relate to methods and systems for electromagnetic surveying.
2. Description of the Related Art
The following descriptions and examples are not admitted to be prior art by virtue of their inclusion within this section.
Electromagnetic surveying of subsurfaces, such as hydrocarbon reservoirs, measures induced electric and magnetic field strengths. The measurements are used to derive an image of the electrical resistivity of the subsurface. This survey technique is typically performed using a marine cable (towed or stationary) and a sensor system deployed from a marine survey vessel. This technique may also include the simultaneous use of a controlled electromagnetic source deployed from the same and/or a different survey vessel.
Typically, electromagnetic measurements are performed by deploying a stationary electromagnetic receiver unit or system on the seafloor. Receiver units are generally equipped with electric and magnetic field sensors, digitizing units, a clock, memory and a power supply. Sea-bottom electromagnetic systems may include a seabed cable deployed from a survey vessel. In addition to the equipment generally found on the aforementioned receiver units, the seabed cable may include a centrally-controlled power supply and a means of data telemetry.